Years ago there was a red '70 Boss @ Willow Springs Raceway and he had 2 Inline 875s on a modified Weber intake. I don't know if he was having engine or tuning issues, however the car was a dog. I would make the assumption it was in the carbs..way too small for an IR set up.

So would 2 of the smaller 'A' carbs at 835cfm each work better when tuned with an IR intake at around 302 CID?

The 9510A Inline carbs (875 cfm) have 1 11/16â€ butterflies and the venturi diameter is 1.6â€. That would be 43mm bores and 40mm choke compared to a 48mm IDA wit 40mm chokes. Also, the boosters in an Inline are bit bulky and crude compared to an IDA so they probably take up more bore space. Hard to say about their efficiency as a booster. There are those who feel that 48 IDAs are a bit on the smallish side. That would make a pair of 9510A Inlines very much so. From my experience 48 IDAs can be limiting on 351 CI engine and for certain when your North of 400 cubes. I would not recommend the â€œAâ€ carbs for IR use. Best leave that to the larger â€œBâ€ carbs. You need good progressive linkage for the bigger Inlines because a little bit of rotation opens a lot of bore area and that means twitchy off idle and low rpm behavior.

Quote

I heard that a Weber intake can be adapted to the Inline Autolites... but how does that work, I wonder?

The bore spacing on an inline carb is the same as sbf cylinder spacing, 3.38â€. The bore spacing of IDA Webers is 120 mm or 4.72â€. Thatâ€™s why the center two runners (cylinders 3 &4 and 5&6) on an IDA sbf intake manifold are closer together than the outer pairs. To run an Inline carb on a Weber IDA intake you need to make adapters that correct the bore spacing and blend the mismatch in bore diameters.

Itâ€™s not too abrupt of a transition to make in Â¾â€-1â€ or so. What Iâ€™ve seen most commonly done is a plate that has the IDA mounting holes with the heads countersunk and then the Inline carb hole pattern drilled in the same plate. Drill some big holes, get out a die grinder to match and blend the bores and you have an adapter. Hereâ€™s an example of adapting a 9510A to a Weber IDA intake.Now hereâ€™s a set of adapters I picked up a long time ago made by a talented individual who was determined to run the larger 9510B Inlines on a 48 IDA Weber intake in style. They are the nicest example I have ever seen.

I have an idea Weber 48 IDA's cfm is 330 total (each) so they are well down on the Autolite Inlines. Rodney

Ya-know, we need to make sure it's an apples to apples comparison but the larger Inlines are rated for 1425 cfm dry flow through all four barrels with 1.5 inches of Hg differential pressure. I've never had one on a flow bench to verify it but it is the factory data. If a 48 IDA can flow 330 cfm under similar conditions that would be pretty darn good (1320 cfm equielant for 4 barrels) when you consider the butterflies on a 48IDA only have about 84% the area of the bigger B-carb which would suggest only about 300 cfm per barrel on the IDA. But it's really about the choke/venturi diameter. The Venturis on the "B" carbs are 1.8" (~46mm) so they should have a bit more flow potential than a 48 IDA depending upon choke size. Like the IDA, the venturis are a seperate part on an Inline and can be modified as well.

Kelly, At the same time we need to remind people that rated airflow is the "maximum capacity" under ideal conditions and if an engine doesn't create enough vacuum (or signal as you and I use) it will only "pull" what it needs. Far too many people do not understand the BASIC principles of a venturi design carburetor. Venturi sizes closely matched to engine size make it easier to maintain the correct air/fuel ratio throughout the power range of the engine. Too large a venturi or carburetor on an engine will still ONLY take in the SAME amount of air as a smaller carburetor (provided it's not TOO small). These whiz-bang formulas to determin what "size carburetor an engine needs are fine except they do not factor in the actual carburetor dynamics. One carb that flows 600 cfm doesn't necessarily work the same as nor make the same power as another manufacturers carburetor in most cases. Randy

Kelly, At the same time we need to remind people that rated airflow is the "maximum capacity" under ideal conditions and if an engine doesn't create enough vacuum (or signal as you and I use) it will only "pull" what it needs. Far too many people do not understand the BASIC principles of a venturi design carburetor. Venturi sizes closely matched to engine size make it easier to maintain the correct air/fuel ratio throughout the power range of the engine. Too large a venturi or carburetor on an engine will still ONLY take in the SAME amount of air as a smaller carburetor (provided it's not TOO small). These whiz-bang formulas to determin what "size carburetor an engine needs are fine except they do not factor in the actual carburetor dynamics. One carb that flows 600 cfm doesn't necessarily work the same as nor make the same power as another manufacturers carburetor in most cases. Randy

I totally agree. We don't race software or dynos. There's theory, and there's what works. -Sometimes they are the same but there's no substitute for experience and real life results. Have a Happy New Year Randy.

Ahh heck. All this Inline carb talk and the other auction motivated me to put one of my systems up for sale. No offense intended to the owner of the piece in the link above that started this thread if he happens to be a member here, but anyone who is willing to pay $4700+ for that system should lunge at mine. If the one in the link above has been in a box for 40 years as the ad says, there isn't a rubber part on it that would be functional.

The ad also says he was told it was on the Gurney/PJ TA car. I would seriously doubt that but would like any of the folks in-the-know on this forum to correct me if they know differently. Even with the engine lowered as in a TA car I dont think those stacks would be under the hood.

Great stuff. Kelly, I have an early in-line small carb (875 cfm). With "XF" number cast into it. The carb looks like it was sand cast, and has DOFF instead of DOZX on the tag. The serial number is 14 if I can recall correctly. It came from AK Miller back in the early '70's. I bought my Boss car and intake set up from the same owner who got it from Ak Miller. The unique part is that this in-line carb has been modified to a 750 cfm, which I would think is better for a cross boss intake on the street. They made smaller venturies and butterflys, I also got the originals as well. What do you think? I often wonder if anyone else ever changed there cfm? you could tailor the carb to the engine. Yes it's a lot of work, but nothing a lathe and mill couldn't handle. Just my 2 cents.

Hi Guys, Great stuff. Kelly, I have an early in-line small carb (875 cfm). With "XF" number cast into it. The carb looks like it was sand cast, and has DOFF instead of DOZX on the tag. The serial number is 14 if I can recall correctly.

Yes Gus, I have seen some of these early units but less than a handful and only on the smaller version carbs. You have a very early experimental engineering unit. It's likely that these early units were only released to people very close to Ford at the time (not likely sold) and most if not all carried experimental part numbers and were built from temporary tooling. There distinguishing features are noted in the pictures I have inserted below. The most obvious difference is the solid area underneath the throttle arm that couples the throttle plate shafts. The production version is more refined because it is an open architecture in this area whereas the closed sand cast version could gather debris and cause the linkage to bind and stick. You are correct about them being sand cast. If you compare them side by side you will not there are no ejector pin marks as there are on the production permanent mold/die cast tooling. Usually the sand castings only apply to the throttle plate (bottom casting) and the venturi plate (top casting) and the the main bodies (containing the main well) were already hard tooled by that time and have the Ford logo cast in....but not always!

Quote

It came from AK Miller back in the early '70's. I bought my Boss car and intake set up from the same owner who got it from Ak Miller.

Like I said, the early ones were given to the fair-haired children/Ford desciples

[/quote]The unique part is that this in-line carb has been modified to a 750 cfm, which I would think is better for a cross boss intake on the street. They made smaller venturies and butterflys, I also got the originals as well. What do you think? [/quote]

And butterflies? I would noy have though the latter to be necessary. Out of curiosity, did the press in inserts to the bores or were they machined to a smaller diameter from the raw casting? In general though, per my previous comment, yes, 750 cfm is better for a street going Cross Boss and in general that large open plenum does not need the bigger carb flow to handle peak surge as the large plenum can do that. The smaller carb enables a stronger booster signal and more response in the the streetabkle range.

Quote

I often wonder if anyone else ever changed there cfm? you could tailor the carb to the engine. Yes it's a lot of work, but nothing a lathe and mill couldn't handle. Just my 2 cents. Gus

Yes, I've seen it done many times. Most frequently by those who have a 1425 cfm "B' carb and want it to behave like an 875 "A" carb. It doesn't work very well because small rotation of the comparatively large 2.25" throttle plate looks like WOT to a small venturi. I have seen some slightly smaller venturis used with success on the larger "B" carbs in IR on 302-351 CI engines.

Gus, if you ever want that carb gone through, I'll take good care of ya. These historical pieces deserve some respect and can contain some educational surprises for guys like me.

Kelly,Quote "Out of curiosity, did the press in inserts to the bores or were they machined to a smaller diameter from the raw casting?" If I recall they were machined. I will look next time I take it out of storage. Yes I will keep you in mind when I need a rebuild. I have something else to show you about an in-line carb, I will take photos tomorrow. This one will freak you out.

This is an odd one. It a big autolite In-line carb 1425 cfm that I picked up for parts. The man who owned it pass away and his wife sold everything. He was an engineer and he was always modifying this stuff. Along with the In-line came an aluminum block which has all the main metering systems and idle system assemblies inside. He had removed them from the In-line and into this aluminum block with lines going back to the In-line. Plus there are mods all over the carb. Here are a bunch of photos to look and wonder what he was up too.

Thanks Gus. Yup, definitely some new ones there. Tough to say what he was up to but looks like it was more of a engineering development tool for a bench testing than actual use.

He streamlined the entry to the booster a little. Like I said earlier, they are a little crude and occupy quite a bit of real estate in the bore. This can help but care needs to be taken in keeping the behavior of each booster the same, especially in IR. He filled/smoothed the backside of the butterfly where the throttle shaft mounts. That would also promote a little more flow potential. Did you know that throttle shafts on some Inlines were half-round where the throttle plate mounts whereas others have small flat about .090â€ thick for mounting (like in these pictures)? On a 2 Â¼â€ opening this can increase the flow area by ~1/2 square inch. â€“Not trivial when you consider the entire area of the opening with no obstruction is about 4 square inches. Thatâ€™s 12.5%!

I would guess that having the main metering circuit external to the carb may have allowed convenience and fast changes for testing. He may also been able to observe what the fuel was doing and if he made a clear holder, how the emulsion tubes were behaving. I canâ€™t really see any reason for removing it from the carb body for actual use unless he wanted a longer holder and emulsion tube.Interestingly enough, it looks like he chose to keep the fuel inlet circuit unaltered. This is the most fiddled with area on these carbs that I typically see. The usual mods were installing a wall in the main well to partially isolate the two main jets then a slit in the float to straddle the thin wall. I suspect this was to control fuel slosh under hard acceleration/deceleration. Like I said before, fuel starvation could be an issue occasionally but only for extreme conditions and mostly drag and hard core road racers; especially if they were running IR. Iâ€™ve also seen people literally hang a Holley fuel bowl and float/inlet valve system on each main well via a pipe nipple! Attached sort of where the pipe nipple is sticking out in your pictures. Evidently this person thought the problem was main well volume, or possibly flow. I think it is more that latter but for the extreme application only. Remember, the inlines share many parts with a 2100 Autolite 2-Barrel. The seat diameter of the metering valve in the inline is .097â€. You can drill it out or increase fuel pressure to make sure the well stays full on high demand but Iâ€™ve found that even though the recommended fuel inlet pressure is 6 psi, they will start blowing the inlet valve off the seat even with a stock diameter at around 7-8 psi. Increase the seat diameter and/or supply pressure and it happens earlier. If you make these mods you need a bigger more buoyant float so it has more shut off force to apply to the lever arm otherwise it will just fuel all over the place at low demand.

I really donâ€™t know what he was up to on the curb idle. Some very early carbs did not have idle adjustment valves at all. I canâ€™t see the discharge slot (there were two sizes of these two!) on the internal bore so maybe that was the case on this carb.